Components of Partial Resistance to Southern Corn Leaf Blight Caused by Bipolaris maydis Race O in Six Corn Inbred Lines.

Components of partial resistance to southern corn leaf blight caused by Bipolaris maydis race O were analyzed using young plants of six corn inbred lines (H95rhm, R2040, Mo17Ht, H95, H93, Pa91) and compared with the progression of the disease in the field. In the greenhouse seedling tests, the infection efficiency (IE) did not vary among the inbred lines. Lesion area (LA), sporulating lesion ratio (SLR) and degree of sporulation (SP) were differed significantly among them and the resistant lines showed low values of LA, SLR, and SP. The LA values of each line corresponded to the disease progression in the field. The inbred line, H93, showed a moderate resistance in the field but the lesions expanded rapidly in young plants. However, H93 showed a low ability of spore production which might account for the moderate resistance in the field. Estimation of spore production in addition to lesion expansion as components of partial resistance should be performed for the prediction of field resistance using young plants.